387. Qualified duty to approve consent by another.

In any case where:

  1.  

    (1)     a tenancy1 includes a covenant2 on the part of the tenant3 not without the approval of the landlord4 to consent5 to the subtenant's assigning, underletting, charging or parting with the possession of, the premises comprised in the tenancy or any part of the premises6; but

  2.  

    (2)     the covenant is subject to the qualification that the approval is not to be unreasonably withheld (whether or not it is also subject to any other qualification)7,

then, where there is served on the landlord a written application by the tenant for approval or a copy of a written